Cats who suffer from cerebellum problems receive benefit from this type of cart as it stabilizes them and prevents them from falling over on their heads or side. Also some of the common neurological conditions, which are progressive resulting in both rear and front limb disability, benefit from four-wheel carts. Four-wheel carts are provided for in all sizes of our K-9 carts. However, due to the complexities of these dog wheelchairs, we require that pets larger than 40 lbs. visit our shop in Oxford, MD for a final fitting. Once inability to walk on both front and rear limb occurs, we are unable to provide help. But, we recommend that you call us to discuss options for any special needs pets.